Design Of The Radio Frequency Energy Harvesting Circuit In Wireless Sensor Nodes Applications

With the development of the Internet of things,more and more wireless sensor nodes are applied to the Internet of things to obtain the most basic object-related information.As one of the solutions to the power supply of wireless sensor nodes,RF energy acquisition technology is very suitable for a large number of scattered wireless sensor nodes because of its wireless power supply and no battery characteristics,so it has received a lot of attention and research.The RF energy acquisition IC designed according to the RF energy acquisition technology can collect the widely existing RF signal in the environment and convert it into DC power supply for other circuits.It is small in size,low in power consumption and can be integrated.It has important application value and more application scope.In this context,This paper aims at the design of RF energy acquisition IC using for wireless sensor nodes.Firstly,in order to solve the problem of RF energy loss caused by diode threshold,a voltage doubling rectifier circuit based on low threshold voltage Native-MOS is used in the design.The designed voltage doubling rectifier circuit based on ISM 915 MHz frequency band and has a sensitivity of-15 d Bm under the condition of 1 V output voltage and 10 ua load current.Secondly,Based on studying the impedance and impedance matching network of the energy acquisition chip,In view of the rectifier circuit having a different impedance with different input power,the use of fixed matching can not adapt to the change of impedance,which will cause the mismatch of matching network and decreasing of the power transmission efficiency.An automatic impedance matching technique is proposed.The RF energy acquisition circuit with the function of automatic impedance matching is designed.under the input power of-8 d Bm,The output voltage and output power of the energy acquisition circuit can be increased by 1.6 times and 2.56 times respectively,At this point,the overall efficiency of the energy acquisition circuit is 27.2%.In addition,because the automatic impedance matching circuit needs clock signal and reset signal,the on-chip clock circuit and reset circuit are designed.The frequency of the designed clock circuit is between 968 khz and 321 khz due to the process and temperature variation.It enables automatic impedance matching circuit to complete impedance regulation in 399 ?s.In addition,for the power consumption of the automatic impedance matching circuit,a power supply control circuit is proposed,which can cut off the power supply of the automatic impedance matching circuit after automatic impedance matching circui finishing its work,and save energy.latch circuit is applying to latch the matching result.Ensure that the impedance matching network remains the same value after the automatic impedance matching circuit is powered down.Finally,the layout of the energy acquisition chip in this paper is designed by using smic 0.18 ?m process,and the board level PCB for chip testing and verification is also designed.